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Target information enhancement using polarized component of infrared images
Abstract
After a deep study of the principle of infrared polarization imaging detection, the infrared polarization information of target and background is modeled. Considering the partial polarized light can be obtained by the superposition of natural light (unpolarized light) and linearly polarized component while ignoring the component of circularly polarized light, and combing with the degree of polarization (DOLP) and the angle of polarization (AOP), the infrared polarization information is expressed by the multiplying of an intensity factor by a polarization factor. What we have modeled not only can be used to analyze the infrared polarization information visually and profoundly, but also make the extraction of polarized features convenient. Then, faced with different application fields and based on the model, a target information enhancement program is proposed, which is achieved by extracting a linear polarization component in a certain polarized direction. This program greatly improves the contrast between target and background, and can be applied in target detection or identification, especially for camouflage or stealth target. At last, we preliminarily tested the proposed enhancement method exploiting infrared polarization images obtained indoor and outdoor, which demonstrates the effectiveness of the enhancement program.
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Due to the fact that the IR recognition of a target is currently to a large extent limited by IR camouflage techniques, herein a new IR polarization technique is proposed to enhance the IR recognition of a camouflaged target. The polarization properties of a camouflaged target and its background were investigated in the wavelength range of 8 -14 μm under a specified environmental condition. It is found that the polarization contrast between the target and its background is much larger than their intensity constrast, which should be of great importance for improving the performance of IR detectors.
The polarization characteristics and their changes reflect the status of the targets. In this work, the concept and the feasibility of using the polarization detection to characterize space targets were discussed. Then the performance of a polarimetric device applied for space targets detection was introduced. Meanwhile, the results of polarimetric observation on space targets were given and the characteristic of scaled models which were similar to the actual targets were measured, respectively. By comparing the two results, it is demonstrated that the trends of the both polarization characteristics fit well with each other. Therefore, the validity of the polarimetric observation on space targets is confirmed. The polarization characteristics of space targets is revealed, for example, the degree of polarization will increase from 5% at midnight to 23.8% before dawn. Especially, the attitude of the solar panels plays a vital role in affecting the polarization characteristics of the satellites. It is indicated that the polarimetric observation is an innovative method applied for space targets detection and identification.
We introduce a novel longwave polarimetric-based approach to man-made object detection that departs from a more traditional direct use of Stokes parameters. The approach exploits the spatial statistics on two coregistered vertical and horizontal polarization components of the images, where differences of spatial second-order statistics in the bivariate space reveal that man-made objects are separable from natural objects while holding invariant to diurnal cycle variation and geometry of illumination. We exploit the invariant feature using the Bayes decision rule based only on probabilities. Experimental results on a challenging data set, covering a 24-h diurnal cycle, show the effectiveness of the new approach on detecting anomalies; three military tank surrogates posed at different aspect angles are detectable in a natural clutter background. These results yield a negligible false alarm rate as the heating components of the tank surrogates were turned off during data collection.
An expression for the polarized emissivity of a material is obtained with the Stokes vector–Mueller matrix polarization formalism. The result obtained is that thermally emitted radiance might have a circular polarization component. In addition, the emissivity depends only on the reflectance matrix.
Certain experiments had indicated that the polarization of emitted radiation was much more prevalent than had been expected. This paper is intended to present some of the background required to understand the phenomenon of emission polarization, which is not as well-known as it should be. The explanation that the phenomenon involves refraction of all the emitted radiation, advanced by Millikan in 1895, is still accepted today. More recent work, substantiating Millikan’s explanation, is cited.
Modern infrared (IR) imaging systems are sensitive enough to detect weak targets, but background clutter makes the detection difficult. The introduction of an IR polarizer into thermal imaging systems is one of the techniques to improve this low target-to-clutter ratio. The use of polarized IR energy helps to detect man-made objects in complex natural backgrounds. Over the past 4 years, we have investigated the polarization properties of thermal IR radiation (8 - 12 micrometers ). In the course of our work, we have built an infrared imaging polarimeter and participated in field and laboratory experiments. This paper summarizes the results of our work. It includes a brief theoretical background, description of the equipment, and a comparison of our empirical findings with a theoretical model and with results of other researchers.
The polarization of reflected radiation can provide useful information
which could be used in remote sensing applications to help distinguish
different natural surfaces with similar spectral signatures. Yet the use
of polarization has been almost completely neglected in remote sensing
applications partially because of the lack of understanding of the
information contained in the polarization field. In this paper, examples
of the polarization of natural scenes will be presented and the
information contained in the polarization field will be discussed. The
imagery presented was collected by taking sets of four photographs of
various natural scenes using a polarizing filter to detect the
polarization field. The polarization field was analyzed by digitizing
the photographs and processing the results at the Image Processing
Laboratory on the Berkeley campus of the University of California.
Polarization imagery
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